Silver nanoparticle biosynthesis from newly isolated streptomyces genus from soil

This study aimed to green synthesis of silver nanoparticles (AgNPs) by cell lysates of actinobacterial strains isolated from Mersin soils. Also, free-radical scavenging potential, the inhibitory effect, and genotoxicity of synthesized AgNPs were investigated. As a result of the screening study, it was detected that cell lysate from isolate AOA21, which were classified in Streptomyces genus according to 16S rRNA gene sequences comparison, showed higher potential for AgNPs synthesis. The optimum pH, AgNO₃ and cell lysate concentration for AgNPs synthesis were found to be pH 9.0, 1 mM AgNO₃ and 2-fold diluted cell lysate, respectively. The FESEM analysis revealed that the size and shape of AgNPs were 35–60 nm and spherical. The x-ray diffraction patterns displayed typical peaks of crystalline AgNPs at 34.07°, 44.04°, 64.45°, 77.40° and 81.36°. The size of cubic crystalline AgNPs was found to be 9.35 nm. The FTIR analysis showed that the especially protein, peptide and amino acid component in the cell lysates of Streptomyces sp. AOA21 may be responsible in reduction of AgNO₃ and stabilization of synthesized AgNPs. The MIC values of synthesized AgNPs for Bacillus cereus, Klebsiella pneumoniae, Escherichia coli and Staphylococcus aureus were found to be 8 μg ml⁻¹, 16 μg ml⁻¹, 16 μg ml⁻¹ and 32 μg ml⁻¹, respectively. Free-radical scavenging activity of synthesized AgNPs was 8.54%–55.58% at a concentration range of 800–2000 μg ml⁻¹. Furthermore, comet assay showed that synthesized AgNPs did not cause significant DNA damage in Saccharomyces cerevisiae at a concentration of 12.5 μg ml⁻¹ and 25 μg ml⁻¹. (paper)